Peptide-based cavitands (resorcin[4]arenes substituted with histidine and glutamine hydrazides) exist as monomeric species in polar solvents (DMSO and methanol). Upon complexation of fullerenes, the cavitands wrap around the hydrophobic guests forming dimeric capsular shells (as evidenced by DOSY). The self-assembly of the cavitands is based on the formation of beta-sheet-like binding motifs around the hydrophobic core. In a polar environment, these hydrogen bonded structures are kinetically stable and highly ordered as manifested by a 100-fold increase of intensity of circular dichroism bands, as well as a separate set of signals and substantial differences in chemical shifts in NMR spectra. This behavior resembles a protein folding process at the molten globule stage with non-specific hydrophobic interactions creating a protective and favourable local environment for the formation of secondary structures of proteins.

The formation of structurally defined bioconjugates of proteins hinges on their regioselective modification. Toward this goal a novel method is described here using the commercial IgA protease to attach a nonnatural peptidic moiety to the N-terminus of predisposed proteins by means of a kinetically controlled reverse proteolysis in water. The process requires an H-Ala-Pro N-terminal sequence and then furnishes a selectively modified conjugate under nondenaturing and nondestructive conditions in acceptable yield. The method lends itself to the N-terminal introduction of orthogonal moieties that may be elaborated further.